In my work for transit agencies, I'm always insisting that reports should not just explain how routes perform (typically in ridership per unit of cost) but also why.

Here's one partial example from an infographic developed by TransLink, the transit agency in Vancouver, Canada.

All other things being equal, long, straight routes perform better than short, squiggly and looping ones. The reasons are obvious to most transit riders (and are laid out in detail in Chapters 4 and 14 of my book) but you'd be amazed how many well-intentioned people haven't figured this out, and continue to advocate land use patterns that make effective transit impossible. (Mantra: It's not Transit-Oriented Development unless it's oriented toward transit that can succeed.)

Now, TransLink can use this in their explanation whenever someone demands that a route should squiggle to serve their interests.

A core of my own practice is in developing ways to build understanding of the causes of transit's success, so if your transit agency is struggling to explain productivity, put them in touch with me!

Spokane Transit (Washington USA) has a new network map out that is one of the clearest I've ever seen. It carefully delineates not just frequent services from infrequent ones, but also presents cases where basic infrequent lines combine to form frequent segments, and ensures that peak commuter express services are visible but can't distract from the clear all-day pattern. The whole thing in its full glory is here: Download Spokane 2011 map. The legend, too, is both clear and wonkish at the same time.

Congrats to Spokane Transit for designing this map for the public.

Full disclosure: I was the lead planner on a restructuring study for Spokane Transit back around the turn of the century, and if I remember right, our project invented the continuous two-way frequent loop of Lines 33 and 44. (The loop is closed on the west side as Line 20, as shown on the full PDF.) Despite many excellent improvements (and some sad service cuts) since then, it's great to see it still operating.

This kind of two-way loop is often useful as a way to combine radial lines and grid elements into a single service. Line 33, for example, intersects Line s 24, 25, and 90 in a grid manner, one line north-south and the other east-west, allowing for a range of L-shaped trips via a connection at this point. However, Line 33 also flow through so that the same segments can also be experienced as radial; if you stay on the bus, you'll get downtown eventually, and to a lot of other useful destinations.

I sometimes caution against excessive attachment to loops. In some contexts, with far more financial resources, I might applaud the breaking up of this loop, as I did of London's Circle Line. Given the extreme financial pressure on US transit agencies, though, I would contend that Spokane's frequent loop was an efficient solution, maybe even an elegant one.

UPDATE: The next post on the Spokane map, looking at colorblindness issues and comparing the map to Portland's, is here.

It imagines a network of rapid transit subways many of which flow into surface rail lines, so presumably a model similar to San Francisco or Brussels or the Boston Green Line.

(He calls it a "tram-train" system, but it's actually the opposite of the pattern used by the celebratedtram-trains in Karlsruhe, because here "train" means a subway flowing through the center of the city, while in Karlsruhe the tram portion is the city and surface train lines are used to reach outer suburbs.)

Some problems to note even in a proposed utopia: Subways that flow into streetcar lines are often a poor fit, for three reasons:

Subways are very high capacity and streetcars usually lower, if only
because you physically can't run streetcars as frequently as you can
run subways. In both San Francisco and Brussels, the subway service
branches onto two or three streetcar branches, and that manages the
problem somewhat. But alas:

Streetcars in mixed traffic are exposed to many causes of delay, subways are not. Since a line is only as reliable as its least reliable point, the full capacity potential of the subway can never be used because cars are flowing in from the streetcar portion at unpredictable times.

Subways are very fast and streetcars very slow. It's rare for a demand pattern intense enough to require a subway to end so abruptly that the only thing you need are streetcars. In both San Francisco and Brussels, the feeling is that if a subway has to transition into a surface light rail form, it should ideally go into exclusive right-of-way so that it's still somewhat fast, and then perhaps transition to streetcar further out as loads are lower. (The M-line in San Francisco tries to do this.) Of course, this is not precisely what happens in either San Francisco or Brussels, because like all systems they are prisoners of the long-ago design of their infrastructure, and the city has grown in so tightly around the infrastructure at it is that it would be unimaginably expensive (in political pain as much as money) to change it.

All these issues will be familiar to transit riders in San Francisco and Brussels.

Note also that ending routes in one-way loops, as this fantasist does, is not the best practice unless the loops are very small (e.g. one block wide). That's because you need a driver break and recovery point at the end of the line, and you want the vehicle to be empty at that point. If you're ending in a large loop (planners sometimes call them "balloon loops") you have the same problem as the London Circle Line: there's never a point where everyone is off so the driver can have a rest and the vehicle can get back on schedule if it's a bit late. Even driverless systems need some spare time at end of line to recover from delays.

One of the world's most famous continuous loops is finally reaching an endpoint. The London Underground's Circle Line, which has long attracted tourists with its simplicity but bedeviled its operators with lack of rest, is to be broken apart into a "tadpole" shape, with trains leaving the circle at Paddington, via a spur of the current Hammersmith & City Line, to end at Hammersmith.

As discussed here, loops touch deep things in the human psyche. Nobody wants to reach the end of the line, really, except for the transit operator. In fact, the "end of the line" shows up fairly often as a metaphor for death. So at many scales, from the London Underground to tiny downtown circulators, there's a constant temptation to offer services that never end, services running in continuous circles. Few people actually want to travel in circles, but the embracing quality of circles, and perhaps the subtext of forgiveness in the notion that life will eventually bring you back to anything that you missed, keeps causing them to appear, not just in plans but in operations. Montréal is the latest to propose a giant continuous loop in its subway system.

Why did the Circle Line come apart? Because it was hard to operate reliably. Reliability depends on regular breaks that give a late service the opportunity to catch up to its schedule. Human drivers obviously need breaks too. Actually, the transit industry usually distinguishes between two kinds of break:

Layover is the time a human driver needs at the end of a line, to do personal business, meditate, snack, whatever.

Recovery is spare time in the schedule whose purpose is to enable a late vehicle to get back on time.

Many labor contracts and operations policies have complex formulas governing these two things, but in broad terms, a bus or tram in mixed traffic needs at least 10% of its time to be layover and recovery, and often closer to 15%, while exclusive right-of-way services may need a bit less.

And since nobody wants to be waiting on the vehicle while these breaks occur, efficient transit lines have endpoints where the vehicle will be empty. Most transit lines that are presented as continuous circles have some provision for this, but it's often awkward. On the Circle Line, drivers took their breaks by leaving the vehicle and taking over one a few minutes later, a method called "operator fallback," which provided layover but didn't solve the problem of recovery. Now that they have both, they should see better operations, and perhaps even happier drivers.

In a recent post I argued that downtown shuttles aren't of much use unless they're extremely frequent. The Detroit People Mover doesn't have that problem; it runs every 3-5 minutes. It has the other common problem of downtown shuttles: it's a big one-way loop.